Apparatus for refining of steel melts

Abstract

Apparatus for treating molten metal comprising a ladle for containing a molten metal to be treated having an upper edge, a hood arranged above the ladle and comprising a heat shield essentially covering completely the ladle and having a ceramic lining facing the molten metal in the ladle, with the heat shield and the upper edge of the ladle being spaced from each to define a gap between the heat shield and the upper edge of the ladle. A screen forms and all-enveloping roof over the heat shield and extends over and below the gap to define a circumferential opening between the screen and the ladle below the gap, and spacing means extending between the screen and the heat shield are provided for maintaining the screen and the heat shield spaced apart with respect to each other to define a chamber between the screen and heat shield. The gap communicates with the chamber for the passage of gases therethrough from the ladle to the chamber, and the circumferential opening defines an inlet opening for ambient air to the chamber. At least one lance means is provided for introducing at least one gas in the molten metal in the ladle and/or to a ladle area above the molten metal, and at least one exhaust means communicating with the chamber is provided for exhausting gases which pass from the ladle area above the molten metal into the chamber through the gap, and also for exhausting air which is sucked from the ambient atmosphere into the chamber mainly through the circumferential opening. At least one aperture means is provided in the hood for lowering at least one of the lance means into the ladle.

I claim: 
     
       1. Apparatus for treating molten metal, said apparatus comprising: a ladle for containing a molten metal to be treated, said ladle having an upper edge;   a hood arranged above said ladle, said hood comprising a heat shield essentially covering completely said ladle and having a ceramic lining facing said molten metal in said ladle, said heat shield and said upper edge of said ladle being spaced from each other to define a gap between said heat shield and said upper edge of said ladle;   a screen forming an all-enveloping roof over said heat shield and extending over and below said gap to define a circumferential opening between said screen and said ladle below said gap;   spacing means extending between said screen and said heat shield for maintaining said screen and said heat shield spaced apart with respect to each other to define a chamber between said screen and said heat shield, said gap communicating with said chamber for passage of gases from said ladle through said gap to said chamber, said circumferential opening defining an inlet opening for ambient air to said chamber;   at least one lance means for introducing at least one gas into said molten metal in said ladle and/or to a ladle area above said molten metal;   at least one exhaust means communicating with said chamber for exhausting gases which pass from said ladle area above said molten metal into said chamber through said gap, and also for exhausting air which is sucked from ambient atmosphere into said chamber mainly through said circumferential opening; and   at least one aperture means provided in said hood for lowering at least one said lance means into said ladle.   
     
     
       2. Apparatus according to claim 1 wherein said at least one aperture also extends through said screen above said heat shield, and all space between said screen and said heat shield is arranged to be ventilated by exhaustion through said exhaust means. 
     
     
       3. Apparatus according to claim 2 wherein an injection lance and a gas purging lance can be introduced simultaneously into a ladle space under said heat shield through two lance apertures extending through said hood. 
     
     
       4. Apparatus according to claim 3, wherein one lance aperture is arranged centrally in said hood, and the other lance aperture is displaced towards a side of said hood. 
     
     
       5. Apparatus according to claim 1, 2, 3, or 4, and further including inert gas means for maintaining an inert gas overpressure in said ladle area above said molten metal during injection and thereafter prior to casting. 
     
     
       6. Apparatus according to claim 5 and further including vacuum means for maintaining a vacuum in said chamber. 
     
     
       7. Apparatus according to claim 1, wherein said aperture means are provided in said hood for lowering at least one said lance means into a ladle space under said heat shield. 
     
     
       8. Apparatus according to claim 1, wherein said aperture means is provided in said hood for lowering at least one said lance means into said molten metal in said ladle.